I saw this video on how they did the post digital zooms in the movie 300, at 7:38 into the video:

How to Tell a Visual Story | Technique Breakdown w/ Larry Fong, ASC - YouTube

I actually thought they were post digital, since they have a different look to them compared to in camera, but how do they zoom into the image in post, without the image pixelating? There is one filmmaker who's feature film I helped out on, and when I saw the finished edit later, I saw that he decided to do a post zoom, but you can see pixelation near the end of the zoom of course.

How did they avoid that that in 300 when zooming from one shot to another, to another?

With the 3 different lens angles in sync, I wonder if the morph feature used in premiere to interpolate moves between jump edits in an interview would do this? That's a very useful feature to cope with the usual head and arms shifts when you have a single camera and need to cut bits out of a talking head.

However, if you shoot in 4K, and zoom to 1080 size, it's pretty artefact free, so if that covered the wide to medium change, and then you did it again to get into the narrow shot, that would seem to be a way forward? Without three identical cameras, though, I can't try it to see.

How did they avoid that that in 300 when zooming from one shot to another, to another?

It's nearly all digital post comps where they start of with a very large comp and can zoom in with no loss. That was all done by Zareh Nalbandian's team at Animallogic here in Sydney, Vancouver or LA. They issued a video showing how the CG layers were composited.

300 - Shot Breakdown - YouTube

Chris Young
Sydney